TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 54 (No. 12), pp. e9-e12, 2002


Small electric and magnetic signals observed before the arrival of seismic wave

Y. Honkura1, M. Matsushima1, N. Oshiman2, M. K. Tunçer3, . Bari3, A. Ito4, Y. Iio2, and A. M. Iikara3

1Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551, Japan
2Disaster Prevention Research Institute, Kyoto University, Kyoto 611-0011, Japan
3Kandilli Observatory and Earthquake Research Institute, Boaziçi University, Istanbul 81220, Turkey
4Faculty of Education, Utsunomiya University, Utsunomiya 321-8505, Japan

(Received September 10, 2002; Revised November 14, 2002; Accepted December 6, 2002)

Abstract: Electric and magnetic data were obtained above the focal area in association with the 1999 Izmit, Turkey earthquake. The acquired data are extremely important for studies of electromagnetic phenomena associated with earthquakes, which have attracted much attention even without clear physical understanding of their characteristics. We have already reported that large electric and magnetic variations observed during the earthquake were simply due to seismic waves through the mechanism of seismic dynamo effect, because they appeared neither before nor simultaneously with the origin time of the earthquake but a few seconds later, with the arrival of seismic wave. In this letter we show the result of our further analyses. Our detailed examination of the electric and magnetic data disclosed small signals appearing less than one second before the large signals associated with the seismic waves. It is not yet solved whether this observational fact is simply one aspect of the seismic dynamo effect or requires a new mechanism.
key words: Izmit earthquake, seismic dynamo effect, seismic wave, electric and magnetic changes.

Corresponding author E-mail: yhonkura@geo.titech.ac.jp

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